Control system for gyro verticals



Sept. 2, 1952 s. KELLOGG,1I., Erm. 2,608,867

CONTROL SYSTEM FOR GYRO VERTICALS S. KELLOGG, '11., EI' AL CONTROL SYSTEM FOR GYRO VERTICAL-S Sept. 2, 1952 Filed March 7, 1947 Patented Sept. 2, 19`52 UNITED STATES PATENT OFFICE CONTROL SYSTEM FOB GYR VERTICALS Spencer Kellogg, 2nd, Glen Head, Robert F. Hays,

Jr., Syosset, and ClareA E. Barkalow, Huntington, N. Y., assignors to The Sperry Corporation, a corporation of Delaware Application March 7, 1947, Serial No. 733,250

K 23 Claims. 1

The present invention relates to a control system for gyro verticals for high speed aircraftf All gyro vertical instruments are subject to certain errors in the reference they provide of the true vertical. With the trend towards higher speedsin aircraft, these errorsreach such a magnitude'that present gyro verticalinstruments do not always provide an accurate attitude reference or representation of the craft relative to its fore and aft and athwartship axes.

The primary object of the present invention is to so improve agyrovertical that it provides (ci. I4-,5.34)

Vli)

an accurate reference for high speed aircraft,

data concerning the heading of the craft and a means for providing signals for the system in accordance with the speed of the wind, the direction of the wind, and the latitude of the craft.

Our improved gyro vertical system is compensated both for the effect of centrifugal force and linear acceleration on the pendulous reference .by the employment of a novel gyro compensated pendulum of the type shown in U. S. Patent No.

2,595,268, issued May 6, 1952, to Spencer Kellogg, y

2nd, oneof the present applicants.

Coriolis acceleration is corrected for at the gyro compensated pendulum of the system.

The gyro vertical is corrected for the effect of the horizontal component of the earths rotation.

The gyro vertical of the system is further coinpensated for drift due to the speed of thecraft over the Vcurved surfaceof the earth which is sometimes referred to as the earths profile correction.

The gyro vertical of the improved system is a non-pendulous instrument, and therefore is not effected by the noted Coriolis, fore and aft or turn accelerations. f

Coriolis acceleration asf'herein defined, is a defiecting force on a pendulum due to the vertical component of the earths rotation (which is proportional to the sine latitude (sine L) and the instantaneous vvelocity of thercraft over the earths surface. The effect of such an acceleration on a pendulum (such as utilized in the improved system in which the same provides a gravity reference for the gyro vertical) is to make the pendulumhang with its lower end slightlyV to the right or' left of `truly vertical in a plane at right angles to the heading of the craft. In the northern hemisphere, the referf ence is displaced to the right hand of a person lookingin the directiorrof travell ofthe craft'.`

The displacement occursto the left hand when the craft is in the southern hemisphere. One of the objects of the present invention is to'compensate the reference of the improved gyro vertical control, system for error therein due to horizontal Coriolis acceleration.

Another featureof the invention is provided by the improved meansY for damping the gyrol compensated pendulum with respect to space coordinates, as determined by the gyro vertical.

Still another feature of the invention comprises the means provided herein for effecting operation of the erecting means at the gyrovertical. l

A further feature of the invention resides in the means utilized for correcting the gyro vertical for' the ground speed of the craft over the curved surface of the earth.` To obtain this correction the effect of the Velocity of the Wind on the craft is taken into consideration.

The invention in another of its aspects relatesy to novel features of the instrumentalities described herein for achieving the principalobjects. of the invention and to novel principles employed.

in those instrumentalities, whether or not these features Vand principles are used for the. saidv principal objects or in the said field.

A further object of lthe invention is to provide Y improved apparatus and instrumentalities embodying novel features and principlesy Aadapted forvuse in realizing the above objects and also adapted for use in other fields.

Other objects, features and structural details of the invention will be apparent fromthe following description when read in relation tothe accompanying drawings, wherein: f Y

Figs. 1A and 1B show a system embodying the Y present inventive concepts in which the elements Fig 2 is a vector diagram used in conr'iection y wlth the description of Fig. 1B of the invenY- tion; and

Fig. 3 is a section vewof the gyro compensated f pendulum taken on line V3'.",'in Fig; 1A.

With reference to Fig. 1A of the drawing, a gyro vertical as indicated at I0, is shown to include a casing or housing I I that is suitably fixed to an aircraft (not shown) whose longitudinal or fore and aft axis is represented by the line I2. The gyro vertical, per se, includes a rotor case or frame I3 whose rotor (not shown) is spun about a substantially vertical axis by suitable means known in the art. As shown, thecase I3 is universally supported on casing Il by a gimbal ring I 4 in a conventional manner. The major horizontal axis of support of the rotor case I3 of the gyro vertical as indicated at I5 is preferably parallel to or coincident with the fore and aft or longitudinal axis of the aircraft on which the system is employed. The minor horizontal axis of support of the rotor case of the gyro vertical as indicated at I6 is preferably parallel to or co-r incident with the pitch or athwartship axis of the aircraft. Rotor case I3 is universally mounted on casing II in neutral equilibrium so that there is no error caused therein by acceleration effects due to Coriolis, turning of the craft about its vertical axis or change in speed of the craft. A pickoif I1 of the selsyn type is indicated at the pitch axis I6 of the gyro vertical. As shown, the rotor of pickoff I1 is connected to the case I3 and is energized from a suitable source of alternating current electrical energy as indicated at I8. The stator of pickoif I1 is suitably fixed to the gimbal ring I4 of the gyro vertical. The instrument also includes a pickoif 20 of the selsyn type at the roll axis I5. Pickoff 20 includes a rotor that is connected to the gimbal ring I4 and energized from a suitable source of electrical energy 2I. The stator of pickoif 20 isconnected to the casing or housing II of the gyro vertical.

The rotors of pickoffs I1 and 20 are stabilized by the gyro vertical While the stators thereof move withmovement ofthe craft from the reference position about its respective pitch and roll axes. With the craft in its reference position, the pickoifs I1 and 2|)v produce a null output. When this position is departedvfrom, the .pickoffs operate, if so connected, to provide an output whose magnitude depends on the extent of the departure and whose phase depends on the direction of the departure or, if connected to .anotherselsyn to position the axis of an alternating magnetic fieldin the second selsyn parallel to the rotor in the first selsyn.

The gyro vertical also includes erecting means in theform of torque motors 22 and 23. These motors` may have a construction similar to that of a two-phase induction motor with a squirrel cage rotor such as shown in Fig. '1 of U. S. Patent No. 2,392,370 to Esval et al. As hereinafter described, the gyro vertical is compensated for the earths rotation and for the true ground speed fis herein termed agyro compensated pendulum v which may be physically dissociated from the gyro vertical. This device is indicated generally in the drawing at 26. The reference device 26 includes a casing 21 that is suitably nxed in po sition on the craft at a point as near as possible to the crafts center of gravity. This point may or may not be remote from the location of the gyro vertical on the craft. In any event, the gyro vertical and its reference device 2B are to be considered as separateelements of the improved system. VAs shown in Figs. lA and 3, device 26 provides a pendulous element 28Y that is universally mounted in casing 21 for movement about an axis 30 parallel to the fore and aft axis of the craft and an axis 3I parallel to the athwartship or pitch axis of the craft. In the device 26, the pendulum is formed as a part of a gyro rotor'case 32 whose minor horizontal axis in gimbal ring 33 corresponds to axis 3I and Whose major horizontal axis corresponds to axis 30. The gyro rotor 34 of device 26 in rotor case 32may be considered to be mounted on the pendulum to spin about an axis coincident with the athwartship axis 3| of the pendulum. Rotor 34' is driven bya suitable motor. at a speed proportional to the true airspeed of thecraft on whichthe system is employed. Thestator wind-i ings of the motor employed for this purpose are indicated at 35 in Fig. 3.

As shown, the gravityV reference device 26 fur- .l ther includes a pickoi 3B of the selsyn type` at.

axis 3i and a pickoi 31 of the-selsyn type at axis 3U. The stator of pickoff 36 is. xedto the gimbal ring 33 and the rotor of this pickoifis adapted to move with the movement of thecase.

32 or pendulum 28 about axis 3l as vthe same is xedly connected thereto. pickoif 31 is mounted on the casing 21 while the rotor of this pickoi is fixedly connected Yto the ring 33 to move with the case 32er pendulum 28V In this instance, motor38is adapted to exert a dampingtorque on the rotor case 32 or pendulum 28 about axis 3I and motor 4I!l is adapted to perform a similar function about axis 30 of deel vice 26.

The gyro 32 operates to correct Ythe Ypendulum y for errors due to the effect of Yaccelerations both when the craft is turning about its vertical axis or changing speedalong its fore and aft axis.

When the craft turns about its vertical axis, th`evr centrifugal force on pendulum 28 tending to tip the gimbal ring 33 out of ahorizontal plane, i. e.,' to turn it about axis 30, produces Ajust 'suiiicientg-Y torque to precess gyro rotor 34 about a vertical axis at the saine rate that the airplane is turning for a predetermined air speed. Viewed from a diierent standpoint, the tendency of the gyro to precess during a turn is opposed by an equal'y and opposite centrifugal force `acting on the pendulum which would otherwise cause it to swing out to the vertical. With acceleration'k or deceleration along the fore and aft axis ofthe t craft, the pendulum'tend's to swing' about axis 3I. This tendency is resisted by a compensating torque applied to the pendulum due to a cor'- related change in speed of the gyro rotor 34;' In

both of the noted conditions, the pendulum Y28' of the reference device 26 maintains its average position truly vertical. For a more detailed description ofthe manner of operation ofthe gyro' compensated Apendulum device 26, reference" is made togthe Ahereinbefore noted Patent No. 2,595,268 based on-the improved gyro compensated-pendulum per se. Y'

In accordance with-the improved system," the The stator of roll.

gyro vertical is slaved to the reference device 26 by comparing the position of the pendulum and the gyro vertical about their fore-and-aft and transverse axes, and applying torques to the gyro vertical upon departure of their proper relationship to erect the gyro vertical. For this purpose the output of the pickoff 36 at axis 3| of the reference. comb-ined with the output of a similar pickoff |1 on the gyro vertical, produces a signalcontrolling the erection of the gyro vertical. This is represented by the lead 45 between pickoifs |1 and 36 and by lead 4| from pickoi 36 to torque motor 22, operating through amplifier 42. About the other axis lead 46 is shown as connecting pickoffs 26 and 31 and lead 43 from pickoff 31 combined with that of pickoif 26 controls torque motor 23 through amplier'44. When the rotors of the pickoffs in either system depart from positional agreement, an output is produced to which the proper torque motor at the gyro vertical responds to restore the condition. Device 26 provides a gravity reference to which the gyro vertical is slaved as described. The transmission systems described provide a means for combining the outputs of two pickoffs. The respective torque exerting means or motors 22 and 23 at the gyro vertical may be considered to be responsive to the individual combining means.

As herein shown, the slaving means interconnecting the gyro vertical I0 and reference device 26 may also include -two integrating networks as indicated generally at 41 and 48. Network 41 provides a means forintegrating the output of the transmission system including pickoifs 36 and |1 by tapping lead 4|. The output of network 41 is fed by way of lead 56 to amplifier 42 to supplement the input to motor 22, when a persistent average signal exists indicating a standoff error due to persistent one way drift of the gyro l0. Motor 22 is consequently responsive to the output of the transmission system including pickoffs 36 and I1 and to the output of the integrating network 41. Network 48 operates in a similar manner to control torque motor 23, the output of the same being` supplied to amplier 44 by way of lead 5|. Network 48 is tapped to lead 43 so that the same is energized by the output of the transmission system including pick' offs 31v and 20. As the neutral equilibrium gyro vertical I0 is corrected for earths rotation and the speed of the craft relative to the earth as hereinafter described the average output of the transmission systems described provides a measure of the residual unbalance of the gyro vertical. These signals are integrated by the networks 41 'and'L 48 and fed the torque motors 22 and 23 for the purpose of substantially cancelling such unbalance of the gyro vertical.` K

In accordance with the present invention, the system provides for the damping of the gravity reference or pendulum 28 or pendulous case 32 of the gyro compensated pendulum device 26.v In this connection, motor 38 at the athwartship axis of device 26 is `operated by the output of an amplifler 52 fed from a differentiating network indicated at 53 by way of lead 54. vTheinput to network 53 is obtained from a tapped connection to lead 4| carrying the output of the transmission system including picko-ifs 36 and I1. By this arrangement, the rate of change of the combined output signal of pickoffs 36 and l1 may be used to damp the pendulum about its axis 3|. Motor 38 provides a means responsive to the output of the differentiating network or means for damping the pendulum 28 or pendulous case 32 about its minor axis of support. The pendulum 28 or 6 pendulouscase 32 of device 26 is damped about axis 30 by means of motor 40, amplifier 55 whose output is supplied the motor and a further differentiating network or means indicated generally at 56.which is connected to amplifier 55 by way of lead 51. Network 56 as shown is tapped to the output lead 43 for the transmission system including pickoffs 31 and 2D. In this instance, motor 40 operates responsive to the output of differentiating means 56 to damp the pendulum '28 or pendulous case 32 about its fore and aft axis 30.

In accordance with the invention, means are of the craft. As herein illustrated, the motor driving the gyro rotor 34 is operated from the output of an amplifier 58 supplied from a two phase generator 60 that is directly driven by f shaft 6| driven at a speed proportional to the true air speed of the craft, which is represented diagrammatically as a true air speed meter device 65, which is well known in the art. As herein shown, device 65 is also connected to drive a 400 cycle generator 10 of the type shown in the patents to Riggs, 2,115,086, dated April 16, 1938 or 2,206,920, dated July 9, 1940, to provid-ea signal proportional to the true .airspeed of the craft. As shown in Fig. 1B, this signal is fed to the primary of transformer 1| by way of lead 12. The secondary of transformer 1| provides a signal that is .represented in Fig. 2 by the vector Vs depicting the true air speed of the craft. The direction of vector Vs is along the fore and aft axis |2 of the craft 13 shown in Fig. 2. The athwartship axis of the craft is indicated at 14. Device 65 and generator 16 provide a means for producing a signal in accordance with the true air speed of the craft.

A directional baseline such as North is provided for the system for the determination of the trueY heading of the craft by means such as. a flux valve compass system (not shown) of the character shown and described in Patent No. 2,383,461 issued August 28, 1945. The output of this compass system is connected as shown in Fig. 1B to the stator of a selsyn signal generator 15 on the shaft 11 connected by way of lead 16. The actual power for rotating shaft 11 is provided by a motor 88 controlled through a power amplifier 8| Vfrom the signal supplied by generator 15 to move the shaft 11 to a position that represents the true heading p of the craft. As shown, motor 80 is connected to shaft 11 through suitable gears 8| 82. Correction for magnetic variation of the baseline may be set into the system manually by means of knob 83 which sets the stator of the position repeating receiver 15 by way of gears 84, 85 and shaft 86. Shaft 11 may operate a true heading pointer 61 readable in a suitable compass card (not shown) by way of gears 88, 9i] and shaft 9|. The shaft 11 yalso positions the rotor of a resolver of the selsyn type indicated' at 32 through gears 93, 34 and shaft 85. The rotor of the resolver 82 :receives a signal from a selsyn devicev96 which is proportional to the cosine ofl the latitude of the craft. The rotor of device 96 are then .applied through respective amplifiers-f 44 and 42 to the torque motors 23v and 22 at the aces-,seri 1 gy-roY vertical to `completely correct the same for drift' about the; axes of the gyro due to the horizontal' component of the earths rotation. Lead IDI' from one of the windings of the resolver 92 connectswith lead 4I to the amplifier 42. Lead. I02 from the' other of the windings of the resolver 92 connects with lead 43.to the amplifier M. The combination of the directional reference means, theresolver 92 Aand device 96 provide a means for producing corrective signals in accordance with the components of the earths rotation about the fore and aft and athwartship axes of the craft. The horizontal compo-nent of the earths rotation about axis I2 or I5 is corrected by the signal to the torque motor 22` from the described means. The'horizontal component of the earths rotation aboutaxis I6 or I4 is corrected by the signal. to

torque motor 23 from the described means.

The gyro vertical of the system is also corrected for drift due to the speed of the craft around the earth. This correction is similar in nature to the correction for the horizontal comp-onent of the earths rotation. It is due to rotation of the craft about the center of the earth and is sometimes referred to as a correction for the earths prole. 'For accuracy, this correction takes into account the ground speed and track of the craft. The order of magnitude of this correction is about the same in extreme instances as the correction due to the earths rotation. For example, if the craft is travelling at a speed of 700 miles per 'hour with a tail Wind of 200 miles per hour, the ground speed is 900 miles per hour Which is about nine tenths of the speed of the earth at the equator where the earths rotation correction on the gyro vertical is maximum.

In accordance with the present invention, the drift of the gyro vertical due to the speed of the craft relative to the earth is corrected for by means including a resolver IBS of the type described for resolver 92. In this instance, the double Wound part of the resolver is positioned by shaft 95 in accordance with the reference position of shaft I'I thereby taking into account the true heading of the craft. The other part of resolver I03 is set manually by a knob IM in accordance with Wind direction as represented at cw in Fig. 2. Vector Vw representative of the magnitude of Wind velocity is set into the system manually through means of potentiometer |05 Whose movable arm |06 is positioned in accordance with the manual setting of knob` IIJ'I. Potentiometer |05 and resolver ID3 are connected by leads |08. Similar to resolver 92, the resolver 'ID3 divides a signal proportional to vector Vw into'components one of which is along the fore and aft axis I2 and the other of which is along theathwartship axis 'I4 of the craft. As represented in Fig. 2, Vwi is the component of wind velocity along axis I2 of the craft and Vwz is the component of wind velocity along the axis 'I4 of the craft. The signal proportional to the fore and aft component of wind velocity is fed by lead IDB to the secondary of transformer 'II Where it is additively combined in this. instance'withthe signal proportional to Vs. The combined signals are fed by Way of lead I i0 to lead Iill and thence to torque moto-r 22 through amplier e2. The signal proportional to the athwartship component of Wind velocity is fed by leads III, II2 to lead |02 and thence to torque motor 23 through amplifier 44. The corrections thus applied to the gyro vertical in this connection'are in accordance with the actual ground track and speed of the 4craft as respectively indicated by the angle 95g andvector Vin Fig. 2. Y

Amplier 44 provides a' combiningmeans for the; athwartship component signals of both earths rotation correction and the crafts speedA correc- Y tion. Amplifier 42. provides a combining means for the. fore and aft component signals ofV bothv earths rotation correction and' the crafts speed correction.

The gravity reference ofthe improved system is corrected for Coriolis acceleration both along the fore-and-afti axis and the athwartship axis.. of the craft. Means are provided for producing signals in accordance with the. component of this acceleration along the fore and aft and athwartship axes of the craft. The signalcorresponding to the fore and aft component of Coriolis acceleration, which acts about the athwartship axis.

is derived from potentiometer H15, resolver |03,`

the directional reference, and transformer'll and is represented by vector V inFig. 2. This signal is fed to a selsyn device II3 by Way of lead II4.

Device II3 multiplies the signal by a factor corresponding to the sine of the latitude of the crafts position. The output of device II3 is fed to torque motor 40 by way of amplifier 55 to effect the necessary correction. 'Lead H5 carries this output.

The signal corresponding to the component of Coriolis acceleration along the athwartship axis (which acts about the fore-and-aft axis) is derived from potentiometer |05, resolver ID3 and the directional reference and is represented by vector Vwz in Fig. 2. This signal is fed to a selsyn device I I6 by way of lead I I'I which connects with lead III. Computing device IIE multiplies the signal by a factor corresponding to the sine of the latitude of the crafts position. The output of device Il is vfed to torque motor 38 by Way of amplier 52 to effect the necessary correction. Lead II8 carries this output. The rotors of devices II3 and IIB are connected to shaft 98 that is positioned manually in accordance with the latitude of the craft.

The vertical component of the earths rotation also has an effect about the fore andaft axis of Y the gyro compensated pendulum 26 acting as a tially double the former and opposite insign.

Therefore, We employ in the output of the Coriolis corrector along the athwartship axis, a halving potentiometer I2ll, which halves the input from device H3 to the amplifier 55, thus applying. a proper correction to the fore and aft axis torquer 40 for both elects. Y Y

Since many changes could be made in the` above construction and many apparently Widely clifferent embodiments of this invention-could be made without departing from the scope thereof, l t

it is intended that all matter contained in the above description or. shown inthe accompanying drawings shall be interpreted as illustrative and not in aflimiting sense.

What is claimed is:

l. In a control isystem'for aircraft gyro verticais, a gravity reference comprising a gyro compensated pendulum having a pendulum movable about an axis parallel to the athvvartship` axis of the craft, a gyro rotor mounted'on said pendulum for spinning about an axis coincident with the axis of the pendulum, and a pick-off at theaxis of said pendulum producing .an outputoperable to erect the gyro :vertical upon .variationv in theand pendulum. f I

2. In a control system for aircraft gyro verticals. a gravity reference comprising a gyro compensated pendulum having a pendulum movable about an axis parallel to the'fore and Yaft axis of the craft, a gyro rotor mounted on said pendulum and spinning about a normally horizontal axis parallel toy the athwartship axis of the craft, and a pickoffy at the axis of said pendulum producing an output operable to erect the gyro vertical upon variation inthe relative vertical positions of said gyro vertical and pendulum.

3. In a control system for aircraft gyrol verticals, a gravity reference comp-rising a gyro compensated pendulum having a universally mounted pendulum movable about normally horizontal axes parallel to the athwartship andtfore and aft axeslofr the craft, a gyro rotor mountedon said pendulum and spinning about an axis coincident with the athwartship axis of said pendulum, and

a pickoif at the fore and aft axis'of said pendulum producing an output and a piclroif` at the rotor mounted on said pendulum spinning aboutv an axis coincident with the athvvartship axis of the pendulum at a speed in accordance with the speed of the craft, a pickoff at the fore and aft axisrof the pendulum, a pickoff at `the athvvartship axis of the pendulum, and erecting means at said gyro vertical responsive to the outputs of said pickoffs.

5. In a control system for aircraft gyro verticals, a gyro vertical having a rotor frame pivotal- 1 ly mounted about an axis parallel to theathvvartship axis of the craft, a gravity reference for said gyro vertical comprising a gyro compensated pendulum having a vpendulum mountedto move about an axis parallel to the athwartship axis of the craft, a gyro rotor mounted on said pendulum and spinning about an axis coincident With'the athwartship axisof the pendulum, a rst pickoff at thev athwartshipaxis of the rotor-frame of the gyro vertical, a second pickoi at the athwartship axis of the pendulum, a comparator system including said rst and second pickoffs, and torque exerting .means at the gyro vertical reponsive to the output of said comparator sys- 6. A system as claimed in claim 5, which includes means for integrating a portion-of the output of said comparator. system, and. said torque exerting means is responsive to the output of the comparator system and the integrating means. l

'7. In a control system for aircraft gyro verticals, a gyro vertical having a rotor case pivotally mounted about an axis parallel to the fore and aft axis of the craft, a gravity reference for said gyro vertical comprising a gyro compensated pendulum having a pendulum mounted to move about an axis parallel to the fore and aft axis'of the craft, a gyro rotor mounted on said pendulum and spinning about a normally horizontal. axis parallel vto the athwartship axis of the craft, a

,first pickoffat the fore andlaftaxis of the' rotor kcase of thel gyro, vertical, a secondpickoff at the L; forey and aft axisof the pendulum, a comparator system including said rst and second pickoffs, and torque exerting means at the gyro vertical responsive to the output of said comparator system.

8. A system as claimed in claim' 6, which includes means for integrating a portion of the output of said comparator system, and said vtorque exerting means is responsiveto the output of the comparator system and the integrating means.

9. In a system ofthe class described, the combination of a pendulum movable about an axis. a gyro vertical having a rotor frame pivotally mounted about an axis parallel to or coincident with the axis of thel pendulum, a pickoff at said gyro vertical and a pick-off at said pendulum, said pick-oii's producing a differential output upon relative inclination of said pendulum and gyroscope about said axis, means for differentiating said output and means responsive to the output of said differentiating means for damp-v ing said pendulum about said axis.y

10. In a system of the class described, the combination of, a pendulum movable about an axis, a first pickoff at said pendulum, a gyro vertical having av rotor case pivotally mounted about an axis parallel to or coincident with theaxis of the pendulum, a second pickoff at said gyro vertical, a signal transmission system including said first and second pickoffs and adapted to produce an output proportional to the departure between said pendulum and gyro vertical, means for differentiating the output of said system, and means responsive to the output of said differentiating means for damping'said pendulum about its axis.

1l. In a system'of the class described, thecombination of, a pendulum universally supported to move about pitch and Vroll axesa gyro vertical having a rotor case universally mounted about pitch and roll axes, a first picko' at said gyro vertical producing an output with departure Vof said rotor case from a null position about the roll axis a second pickoi at said gyro vertical producing kan .outputv `with departure of said rotor case from a null position about the'pitchA axis, means for differentiating the output of said first pickoff, and means responsive to the output of said differentiating means .for damping said pendulum about its roll axis, 'means for differentiating the output of said second pickoif, and means responsiveto the output of said differentiating means for damping-said pendulum about its pitch axis. 'i 12. In a system of the class described, the combination of, a pendulum universally supported to move about pitch and roll axes, a-rst pickoif at said pendulum producing an output with movement of said pendulum from a reference position about its roll axis, a-second pcko at said pendulum' producing an output with movement of said pendulum from afreference position about its pitch axis, a gyro vertical having a rotor case universally mounted about pitch and roll axes, a third' pickoif at said gyro vertical producing. an output .With departure of said rotor case from a null position about the roll axis, a fourth pickoff at said gyro vertical producing an output with departure of said rotor case from a null position about the pitch axis, a first signal comparator Y system including said first and third pickoifs, means for differentiating the output of saidsystem, means responsive to the output of said differentiating means for. damping said pendulum about itsroll axis, a second signal comparator system `including said second and fourth pick- `voffs-means for diferentiati-ng the output of` said second system,and means -responsiveto thefoutput of lsaiddifferentiating means 'for-damping -sai'd pendulum about its pitch axis.

1 3, In a system of the class described, the combination-of, a gyro compensated pendulum including a pendulous gyro rotor case movable about an axis and a gyro rotor supportedby said v'gyro pendulum producing an loutput with departure between said cases from a predetermined relationship about saidY axis, means for differentiating the output of said system, and

v meansY responsive to the output of said dif'- ferentiating means for damping said pendulous Y case about its axis.

14. In a system of the class described, the. combination of, a gyro compensated pendulum including a pendulous gyro rotor caseV movable Y.about an axis and a gyrorotor supported by said case spinning aboutan axis coincident with the axis of said case, a first pickoif at said pendulous case producing an output with movement of said case from a reference position, 'a gyro vertical `lous rotor case aboutits axis.V

15. In a control system of thev class described,

.. an aircraft gyro vertical having a rotor case supported in neutral equilibrium on an axis parallel to the athwartship axis of the craft, means for exerting a torque about the athwartship axis Aof the case, first means including a compass and a resolver for producing'a signal in accordance 'with the component ofthe earths rotation along the athwartship axis of the craft, second means also including said compass and a resolver for producing a signal in accordance Withthe component of wind velocity along the athwartship 'faxes of the craft, andv means for combining the signals of 'saidiirst and second producing means to operate said torque exerting means.

16. In a control system of the class described, a'n aircraft gyro vertical having arotor caseV supported in neutral equilibrium'on an axis parallel to the fore and aft axis of the craft, means for exerting a torque aboutthe'fore and Aaft axis of vthe case, rst means, including a compass and a resolver for producing a signal in accordance "with the component of the'earths rotation along the athwartship axis Yof the craft, second means including a Wind velocity and Wind'direction set 'andan airspeed meter for producing a signal in accordance with the fore-and-aft component; of the ground speed of the. craft, and means for combining the signal of said first and second producing means to Yoperate-saidtorque exerting means. f

17. In a control system of the class described, an aircraft gyro vertical'having a rotor case supported in neutral equilibrium on an axis parallel ktothe fore' and aftaxis of the craft andan. axis parallel to the atliwartship axis of the craft,

means for exerting a torque aboutthe fore and aft axis of the case, Vmeans for producing. a

signal in accordance with the ground speed of the craft for operating said fore and aft torque Yexerting means, means vfor exerting a torque about the athwartship vaxis of the case, `and means for producing a signal-in accordance with the component of Wind velocity along 'the athwartship axis of the craft for operating lsaid athwartship torque exerting means.

18. In a system of the class described, a gravity reference for an aircraft gyro vertical comprising a gyro compensated pendulum having a pendulum with an axis parallel to the atl'ivvartship axis of the craft, a gyro rotor mounted-'on said pendulum spinning about an axis coincident with the axis of the pendulum, means forexerting a .torque about the athvvartshipaxis of the A pendulum, and means forproducing a 'signal in accordance with the component of Coriolis acceleration along the fore and aft axis of the craft to operate said torque exerting means.

19. In a system of the class described, a gravity reference for an aircraft gyro vertical comprising a gyro compensated pendulum having a pendulum with an axis parallel to thefore and aft axis of the craft, a gyro rotor mounted on said pendulum spinning about an'axis parallel to the athwartship axis of the craft, means forv exerting a torque about the fore and aft axis of the pendulum, and means for producing a signal inaccordance with the component of Coriolis acceleration along the athwartship axis of the craft-'to operate said torque Vexerting means.

20. A gyro compensated pendulum, as claimed in claim 19, in which the last-named signal is halved because Vof the partial correction for Coriolis error due to the vertical component of theearths rotation about the fore-and-aft axis of the craft. v

21. In a control system of the class described, an aircraft. gyro4 vertical having a rotor frame supported in neutral equilibrium on an axis parallel vto the fore'and aftaxis of'the craft, meansfor exerting a torque about an axis of Vsaid frame, first means for producing a signal in Vaccordance with the true-air speed of the craft,

second means for producing a signal in accord- .ance with the component of Wind velocity along the fore and aft axis of the craft, and means for combining the signals of said first and second producing means to operate said torque exerting means.

22. The combination of a pendulum mounted on a moving craft with anvaxis of freedom parallel to the fore-and aft axis of the craft, means for exerting a torque about said axis of the pendulum, means for producing a signal in accordance with the component ofCoriolis acceleration along the fore and aft axis ofthe craft, means for halving the signal of said signal producing means, and means for operating said torque exerting means by the signal output of said halvingmeans for correcting the pendulum for the effect thereon of the vertical component of the earths4 rotation and of said Coriolis acceleration.

23. In a control system of the class described, an aircraft gyro vertical having a rotor case supported iny neutral equilibrium on axes parallel to the fore-and-aft and athwartship axes of the craft, means for exerting a corrective torque about the athwartship axis of the case to compensate for the drift of the gyro due to the earthszrotation and to the crafts velocity thereover, rst means including a compass,v a mag- ;netic variationcorrector anda resolver for pro- 13 ducing a signal proportional to the component craft. third means also including said compass and resolver for producing` a signal proportional to the component of the 'wind velocity along -thef fore-and-aft axis of the craft, and means `lfor:` combining the signals of said rst, second andr` third producing means to operate said torque exerting means.

The following references are of file of this patent:

14 v REFERENCES CITED record in the UNITED STATES PATENTS" Number Name Date Fairchild et a1 .Nov. 3, 1925 Anscott et al. gilet.v 18, 1938 Esval -..Aug 18, 1942 Ross July 30, 1946 Ford vet al Noy, 12, 1946' Haskins et al.- Decl 17, 1946 Fischer ..-'Ap'r. 15, 1947-. Poitras Sept. 9, 1947 Libman Feb. 14, 1950V 

